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First of all this isn't a copy of DNS Conditional forwarder returns NETBIOS instead of FQDN (just sounds very similar).

We have two separate domains that do conditional forwarding to eachother. Each of these domains is spread across the same three locations and the naming convention of the host indicates which site the system is at.

For example:

  • dc11.a.com: DC 1 for domain A at site 1
  • dc12.a.com: DC 2 for domain A at site 1
  • dc21.a.com: DC 1 for domain A at site 2
  • dc31.a.com: DC 1 for domain A at site 3
  • dc11.b.com: DC 1 for domain B at site 1
  • and so on.

The DCs at each site have conditional forwarding set up to all the DCs of the other domain at the corresponding site, and the first DC at all sites, so:

dc11.a.com forwards requests to

  • dc11.b.com
  • dc12.b.com
  • dc21.b.com
  • dc31.b.com

All forwarding seems to work correctly, for example if I'm on dc11.a.com I can successfully do a lookup of dc11.b.com.

However.. we've had some strange behavior lately (users reporting that lookups are failing, which I haven't been able to reproduce myself but I've received screenshots of errors) which made me double check the forwarding rules and I've noticed something odd: there are a couple of instances where the FQDN of a forwarded host shows up as a short name instead of the FQDN. So for example on dc11.a.com under the forwarding properties of b.com I see this:

  • 10.1.200.11 dc11.b.com
  • 10.1.200.12 dc12.b.com
  • 10.2.200.11 dc21
  • 10.3.200.11 dc31.b.com

What's also interesting is that the any line that has the short name instead of the FQDN always takes a second or two to resolve when I open the properties window..

I've verified that all hosts do register their suffix in DNS, I've tried ipconfig /flushdns and /registerdns and tried re-adding the forwarding. I've double checked the dns entries for all of the hosts both forward and reverse and they're all the same everywhere. If I do an nslookup of 10.2.200.11 on dc11.a.com against any of the B hosts I get back the FQDN dc21.b.com.

However no matter what I do, in the forwarding properties those problematic hosts always show the short name.

Any suggestions would be greatly appreciated!

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Martin
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  • So I was able to get dc21.b.com to show up with the FQDN in the forwarding properties by adding a reverse lookup zone for 10.2.200.x and adding a PTR record for 10.2.200.11 pointing to dc21.b.com but I don't know why that was needed, there aren't any reverse lookup zones for 10.1.200 or 10.3.200 and those hosts show up with the FQDN.. So I've kinda solved my problem for now but it's ugly and I'd love to find out what the underlying issue is.. not going to mark the question as answered just yet. – Martin Apr 01 '15 at 17:15

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